Abstract: Production apparatus for vapor-grown fine fibers, comprising a vertical furnace and a horizontal furnace intersecting each other in an L-shaped configuration. Raw material and catalyst and carrier gas are injected into the top of the vertical furnace to form fine fibers that fall freely through the vertical furnace and land and rest on a conveyor in the horizontal furnace for conveying the fibers through the second furnace while the fibers grow in size. Gas and fibers are discharged from an end of the horizontal furnace remote from the vertical furnace. The horizontal furnace has second injecting structure injecting material for fiber growth but no catalyst into said horizontal furnace.

Abstract: A process for producing carbon fibers which comprises feeding an inert gas into a vertical furnace at about 500 to about 1,000.degree. C. and into a transverse furnace at about 800 to about 2,000.degree. C. connected thereto so that the inert gas flows from the transverse furnace toward the bottom of the vertical furnace and then to the top of the vertical furnace, and feeding preoxidized fibers from the top of the vertical furnace to pass the fibers countercurrent to the inert gas flow through the two furnaces to thereby carbonize the fibers. Apparatus of the type shown in the drawing for the production of carbon fibers by the above process. Carbon fibers having good performance can be produced with good efficiency.